HIGH-SPEED DETECTION METHOD OF METALLIC ELEMENTS OF DENTAL RESTORATION FROM ALLERGY SUSPECTED PATIENTS BY X-RAY FLUORESCENCE ANALYSIS

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For diagnosis and treatment of metal allergy, it is essential to know the metallic elements composing the restorations in a suspected patient. This research aimed to confirm the hypothesis that microscopic X-ray fluorescence analysis can quickly provide effective information on the metallic elements, in spite of a very small amount of sample collected from the patient's mouth. The sample was collected by rubbing the restorations with the sharp corner of a folded lapping film. The sample like a spot at the corner was analyzed by a microscopic X-ray fluorescence equipment (XGT-2700, Horiba, Japan), which generates X-ray beam of 0.1 mm in diameter. Routine analysis took 8 minutes at most, including collection of the sample from the patient's mouth, charge of the sample, detection of the characteristic X-rays, and final display of the result. Based on the calibration line that was obtained by measuring X-ray intensity from standard gold films, the amount of gold sample on the film was estimated to be several tens nanogram. In the case of such a faint sample, the sensitivity for each element decreases with the increase of its characteristic X-ray energy because of the lack of sufficient information depth. To correct this intensity abnormality, the lapping film was covered with a plastic film before measurement. For typical dental alloys, main components were evaluated within a few percents deviation from the values indicated by manufacture. Furthermore, additive elements of 0.5 % or more, such as zinc, could be detected in high reliability. From these results, it is concluded that the high-speed detection method of metallic elements of dental restoration is very useful for diagnosis metal allergy.